Thermal degradation of trimethylolpropane/adipic acid hyperbranched poly(ester)s

Hyperbranched poly(ester)s offer attractive features for applications in a number of areas, particularly as platforms for the support of controlled release actives in the agricultural and biomedical fields. Such materials have been generated from trimethylolpropane and adipic acid, and fully characterized using chromatographic, spectroscopic, and thermal methods. The thermal stability of these polymers has been assessed using thermogravimetry and infrared spectroscopy. The degradation characteristics of these materials have been compared to those of two linear adipic acid polymers. The prominent feature of the thermal degradation of the hyperbranched poly(ester)s is ether formation while that for the comparable linear poly(ester)s is ester pyrolysis resulting in chain scission.     

Influence on fluorescence properties of hyperbranched poly(amidoamine)s by nano golds

The influence of gold nanoparticles (GNPs) and gold nanodots (GNDs) on fluorescence properties of hyperbranched poly(amidoamine)s (HPAMAMs) which were synthesized by Michael addition of 1‐(2‐aminoethyl) piperazine (AEPZ) and methyl acrylate (MA) was investigated in this study. It was found that GNPs with definite surface plasma absorption can quench the fluorescence of HPAMAMs. With the increasing of the concentration of GNPs, the fluorescence intensity of HPAMAMs decreased correspondingly, and varied linearly at low concentration of GNPs. This phenomenon was owing to the fluorescence resonance energy transfer (FRET) between the HPAMAMs and GNPs. In contrast, the complex with smaller GNDs encapsulated in the interior of the HPAMAMs presented greatly enhanced emission. Those results show that the size of nano golds may be used to adjust the fluorescence properties of HPAMAMs and may extend potential applications of HPAMAMs and GNPs. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Synthesis,electrolyte properties and solar cell performance of hyperbranched poly(aryl-ether-urea)s

Hyperbranched poly(aryl-ether-urea)s with phenyl, N,N-dimethylamino ethyl and polyethylene oxide end-groups linked through urethane group – HBPEU-1, HBPEU-2 and HBPEU-3 respectively – were synthesized from an AB₂-type blocked isocyanate monomer and characterized by FT-IR, ¹H-NMR, SEC-MALLS, TGA and DSC techniques. The molecular weight of the polymers were found to be ranged from 4.9 × 10³ ? 1.96 × 10⁴ g/mol. The TGA results showed that the polymers decompose between 175°C – 220°C. In the DSC curves, HBPEU-1 and HBPEU-3 showed T_g at 160°C and 53°C respectively, whereas HBPEU-2 did not showed clear T_g. All the three polymers were converted into polymer electrolytes by doping with LiI/I₂. The doped polymers showed remarkably high ionic conductivity, up to 222 – 277 times compared to the un-doped polymers and the highest conductivity was observed with doped HBPEU-2. The TiO₂ based dye-sensitized solar cells (DSSCs) were fabricated using the doped polymer electrolytes and their performance was tested; HBPEU-2 showed good performance by yielding energy conversion efficiency (η) of 4.5%.     

Perfectly branched and hyperbranched poly(ether amide)s

Poly(ether amide) dendrimer segments based on 5-(2-aminoethoxy)-isophthalic acid have been synthesized using the convergent approach and mild reaction conditions. The monodendrons were combined to dendrimers via different core molecules and the resulting properties of the molecules were compared to those of the monodendrons. The melt polycondensation of the AB₂ monomers with analog structure resulted first in undefined polymer structures. However, by thermal polyaddition reaction of suitable functionalized oxazoline monomers, well defined hyperbranched poly(ether amide)s with phenol terminal groups could be synthesized.     

Multistimuli‐responsive hyperbranched poly(ether amine)s

Multistimuli‐responsive hyperbranched poly(ether amine)s (hPEAs) were successfully synthesized through nucleophilic addition/ring‐opening reaction of commercial diglycidyl ether and amine via one‐pot synthesis. In aqueous solution, these hPEAs exhibited very sharp response to temperature, pH, and ionic strength, with well‐tunable cloud point (CP). Through changing the poly(ethylene oxide) (PEO) chain content of hPEAs, pH, and ionic strength, the CP could be adjustable from 35 to 100 °C, and increased with the increasing of PEO content, the decreasing of pH and ionic strength. The CP of hPEAs aqueous solution presents a linear relationship to the PEO content in pH range from 6.6 to 8.0. Dynamic light scattering (DLS) investigation indicated that these hPEAs dispersed in aqueous solution to form the stable nanomicelles, whose aggregation can be controlled by temperature, pH, and ionic strength. Moreover, the obtained hPEAs contain reactive amino groups in periphery and hydroxyl groups inside, which can be further functionalized. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4252–4261, 2010     

Thermal degradation of poly(vinylpyridine)s

The thermal stability and the temperature at which maximum degradation yields are detected were quite similar for both poly(2-vinylpyridine) (P2VP) and poly(4-vinylpyridine) (P4VP). However, considerable differences among the thermal degradation products of both polymers were detected indicating a correlation between the polymer structure and the degradation mechanism. Direct pyrolysis mass spectrometry analyses revealed that P2VP degrades via a complex degradation mechanism, yielding mainly pyridine, monomer, and protonated oligomers, whereas depolymerization of P4VP takes place in accordance with the general thermal behaviour of vinyl polymers. The complex thermal degradation behaviour for P2VP is associated with the position of the nitrogen atom in the pyridine ring, with σ-effect.     

Preparation and enhanced properties of poly(propylene)/ silica‐grafted‐hyperbranched polyester nanocomposites

A series of poly(propylene) silica‐grafted‐hyperbranched polyester nanocomposites by grafting the modified hyperbranched polyester (Boltorn? H20), possessing theoretically 50% end carboxylic groups and 50% end hydroxyl groups, which endcapped with octadecyl isocyanate (C19), onto the surface of SiO₂ particles (30 nm) through 3‐glycidoxy‐propyltrimethoxysilane (GPTS) was prepared. The effect of silica‐grafted‐modified Boltorn? H20 on the mechanical properties of polypropylene (PP) was investigated by tensile and impact tests. The morphological structure of impact fracture surface and thermal behavior of the composites were determined by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), respectively. The melt viscosity of composites was investigated by melt flow index (MFI). The obtained results showed that: (1) the modified Boltorn? H20 was successfully grafted onto the SiO₂ surface confirmed by FT‐IR and X‐ray photoelectron spectroscopy (XPS) analysis; (2) the incorporation of silica‐grafted‐modified Boltorn? H20 (3–5 wt% SiO₂) greatly enhanced the notched impact strength as well the tensile strength of the composites; (3) the incorporation of silica‐grafted‐modified Boltorn? H20 had no influence on the melting temperature and crystallinity of PP phase; (4) the MFI of PP composites increased when the silica‐grafted‐modified Boltorn? H20 particles were added compared with PP/SiO₂ or PP/SiO₂‐GPTS composites. Copyright © 2004 John Wiley & Sons, Ltd.     

Thermal properties of novel polymers based on poly(hydantoin-methyl-p-styrene) and their substrates

The following compounds have been synthesized: (a) hydantoins 5,5-dimethylimidazolidine-2,4-dione (1), 1??,3??-dihydrospiro[imidazolidine-4,2??-indene]-2,5-dione (2), 3??,4??-dihydro-1??H-spiro[imidazolidine-4,2??-naphthalene]-2,5-dione (3); (b) monomers: 5,5-dimethyl-3-(4-vinylbenzyl)imidazolidine-2,4-dione (4), 1-(4-vinylbenzyl)-1??,3??-dihydrospiro[imidazolidine-4,2??-indene]-2,5-dione (5), 1-(4-vinylbenzyl)-3??,4??-dihydro-1??H-spiro[imidazolidine-4,2??-naphthalene]-2,5-dione (6), (two of them are unknown: 5 and 6); (c) macromolecular compounds: poly(chloromethyl-p-styrene) (7), used as reference, and three polymers (two of them are novel) obtained by substitution of hydantoins 1?C3 to poly(methyl-p-styrene) (8?C10). Their thermal properties have been studied by thermogravimetry. It was found that the chemical structure, tautomerization, and intermolecular interaction influence the thermal stability of substrates. The presence of phenyl rings causes the increase of resistance of studied hydantoins. The obtained polymers are characterized by significantly improved thermal stability comparing to poly (chloromethyl-p-styrene). The mechanism of thermal degradation of investigated polymers and explanation of their thermal resistance has been proposed. The relatively high temperatures of glass transition of polymers have been determined by DSC.     

Preparation and pervaporation properties of crosslinked hyperbranched poly(amine-ester) membranes

Crosslinked hyperbranched poly(amine-ester) (HPAE) membranes were prepared by crosslinking its terminal hydroxyl groups with glutaraldehyde (GA). The crosslinked HPAE membranes showed high reactivity and good hydrophilicity. The crosslinking degree was investigated by Fourier transformation infrared spectra (FT-IR). Atom force microscope (AFM) and scanning electron microscope (SEM) reveals that the crosslinked HPAE films have smooth surfaces, dense and homogenous matrices. The swelling degree of the membrane was higher in water than that in isopropanol. From the permeation of pure water through the HPAE membrane, the effect of hydroxyl/aldehyde group ratio on the permeation flux and separation factor was investigated. The results indicated that the permeation flux increase was accompanied with the separation factor decrease if the water concentration increased in the feed solution.     

Synthesis and characterization of new hyperbranched poly(aryl ether oxadiazole)s

A new AB₂ monomer was synthesized for use in the preparation of a hyperbranched poly(aryl ether oxadiazole) with terminal phenol functionality. The AB₂ monomer contains two phenolic groups and a single aryl fluoride group that is activated toward nucleophilic displacement by the attached oxadiazole ring. The nucleophilic substitution of the fluoride with the phenolate groups led to the formation of an ether linkage. Subsequently, a hyperbranched poly(aryl ether oxadiazole) having approximately a 44% degree of branching, as determined by a combination of model compound studies and ¹H NMR, was obtained. The terminal phenolic groups underwent facile functionalization, furnishing hyperbranched polymers with a variety of functional chain ends. The nature of the chain‐end groups had a significant influence on the physical properties of the polymers, such as the glass‐transition temperature and their solubility. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3851–3860, 2001     

Structural and end‐group effects on bulk and surface properties of hyperbranched poly(urea urethane)s

The hydroxy end groups of aromatic and aliphatic hyperbranched poly‐(urea urethane)s prepared with an AA* + B*B₂ one‐pot method were modified with phenylisocyanate, butylisocyanate, and stearylisocyanate. The success of the modification reaction was verified with ¹H NMR and IR spectroscopy. Linear model poly‐(urea urethane)s were prepared, too, for comparison. The bulk properties of OH functionalized hyperbranched poly(urea urethane)s, compared with those of linear analogues and modified hyperbranched poly(urea urethane)s, were studied with differential scanning calorimetry, thermogravimetric analysis, and temperature‐dependent Fourier transform infrared measurements. Transparent and smooth thin films could be prepared from all polymer samples and were examined with a light microscope, a microglider, and an atomic force microscope. The properties of the polymer surface were examined by measurements of the contact angle and zeta potential. For all samples, the properties were mainly governed by the strong interactions of the urea and urethane units within the backbone, whereas the influence of the nature of the end groups and of the branched structure was reduced in comparison with other hyperbranched polymer systems. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3376–3393, 2005     

Development of an efficient route to hyperbranched poly(arylene ether sulfone)s

A two‐step route to an AB₂ monomer that underwent polymerization via nucleophilic aromatic substitution to afford hyperbranched poly(arylene ether sulfone)s (HB PAES) was developed. The synthesis of 3,5‐difluoro‐4′‐hydroxydiphenyl sulfone ( 4 ) was accomplished by the reaction of 3,5‐difluorophenylmagnesium bromide with 4‐methoxyphenylsulfonyl chloride, followed by deprotection of the phenol group with HBr in acetic acid. The polymerization of 4 in the presence of 3,4,5‐trifluorophenylsulfonyl benzene or tris(3,4,5‐trifluorophenyl)phosphine oxide as a core molecule afforded HB PAES with number‐average molecular weights ranging from 3400 to 8400 Da and polydispersity index values ranging from 1.5 to 4.8. The presence of cyclic oligomeric species, formed by an intramolecular cyclization process, was a contributing factor to the relatively low molecular weights. The degree of branching (DB) of the HB PAES samples was estimated by a comparison of the ¹⁹F NMR spectra of the polymer samples with those of a series of model compounds, and DB values ranging from 0.51 to 0.70 were determined. The glass‐transition temperatures for the HB PAES samples were in the range of 205–222 °C, as determined by differential scanning calorimetry. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43:3178–3187, 2005     

Synthesis of linear and hyperbranched poly(etherketone)s containing flexible oxyethylene spacers

As an alternative to strong acid reaction media for the Friedel–Crafts acylation for a polymer‐forming reaction, a mild polyphosphoric acid (PPA) with optimized amount of phosphorous pentoxide (P₂O₅) has been tested for the polymerization of AB monomers 4‐(2‐phenoxyethoxy)benzoic acid and 3‐(2‐phenoxyethoxy)benzoic acid, and an AB₂ monomer 3,5‐bis(2‐phenoxyethoxy)benzoic acid. The reaction progress of AB₂ monomer was conveniently traced by FTIR spectroscopy monitoring aromatic ketone (C?O) stretching bands arisen from carboxylic acid groups at the chain ends and carbonyl groups in the backbone as a function of reaction time at 110 °C. The resultant linear and hyperbranched polymers containing flexible oxyethylene spacers, which were prone to be hydrolyzed in strong acids at elevated temperature, displayed high intrinsic viscosities. Thus, the reaction medium PPA/P₂O₅ mixture as an electrophilic substitution reaction was indeed benign not to depolymerize growing polymer molecules but strong enough for the direct generation of carbonium ion from carboxylic acid to promote efficient polymerization. The resultant hyperbranched poly(etherketone) (PEK) displayed the best solubility among samples. All PEKs showed good thermal stability; glass transition temperatures were in the range of 90–117 °C; 5% weight loss generally occurred at greater than 345 °C in air. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5112–5122, 2007     

Synthesis of hyperbranched poly(aryl amine)s via a carbene insertion approach

A novel diazirine functionalised aniline derivative, 3-(3-aminophenyl)-3-methyldiazirine 1, was prepared and employed as an AB(2)-type monomer in the synthesis of hyperbranched polymers; thus providing the first instance in which polyamines have been prepared via carbene insertion polymerisation. Photolysis of the monomer 1 in bulk and in solution resulted in the formation of hyperbranched poly(aryl amine)s with degrees of polymerisation (DP) varying from 9 to 26 as determined by gel permeation chromatography (GPC). In solution, an increase in the initial monomer concentration was generally found to result in a decrease in the molecular weight characteristics of the resulting poly(aryl amine)s. Subsequent thermal treatment of the poly(aryl amine)s caused a further increase in the DP values up to a maximum of 31. Nuclear magnetic resonance (NMR) spectroscopic analysis revealed that the increase in molecular weight upon thermal treatment resulted from hydroamination of styrenic species formed in the initial photopolymerisation or activation of diazirine moieties.     

Synthesis and characterization of ultraviolet‐curable hyperbranched poly(siloxysilane)s

Two UV‐curable hyperbranched poly(siloxysilane)s ( I and III ) containing vinyl and allyl end groups were synthesized via polyhydrosilylation with methylbis(methylethylvinylsiloxy)silane and methylbis(dimethylallylsiloxy)silane monomers. A cationic UV‐curable hyperbranched polymer ( II‐Ep ) with epoxy end groups was prepared via the hydrosilylation of hyperbranched polymer II with Si? H terminated groups and glycidyl methacrylate, and II was also obtained via the polyhydrosilylation of AB₂‐type monomer methylvinylbis(methylethylsiloxy)silane. All hydrosilylation reactions were catalyzed by Pt/C or chloroplatinic acid. Three AB₂‐type monomers were synthesized via the hydrolysis of functional chlorosilane, which was prepared with Grignard reagents and dichlorosilane. The molecular structures of the polymers were characterized with ¹H NMR, Fourier transform infrared, and gel permeation chromatography, and the UV‐curing behaviors of the polymers under different atmospheres and with different photoaccelerators were also investigated. The thermostability of uncured and cured polymers was examined with thermogravimetric analysis, and the data indicated that the orders of the onset decomposition temperatures for the cured polymers and the residue weights were as follows: III (380 °C) > I (320 °C) > II‐Ep (280 °C) and I (70.4%) > III (64.1%) > II‐Ep (60.9%), respectively. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1883–1894, 2005     

Gas transport properties of poly(arylether bissulfone)s and poly(arylether bisketone)s

The transport properties of the poly(arylether bissulfone) based on bisphenol A (PBSF) and the poly(arylether bisketone) s based on bisphenol A (PBK) and bisphenol S (PBK-S) are reported at 35°C. Comparisons are made with the polysulfone and the polycarbonate also based on bisphenol A to determine the effect of the long, rigid bisketone and bissulfone groups on polymer properties. A direct comparison also is made between PBK and PBSF, which differ only by their ketone and sulfone groups. The bulkier sulfone group increases free volume and T_g more than the ketone group. This results in higher solubility and diffusivity coefficients for the bissulfone versus the bisketone polymer, both of which contribute to higher permeability coefficients. © 1993 John Wiley & Sons, Inc.